Method of treating leading-in wire



Feb. 26, 1935. w. P. ZABEL. 1,992,798

' METHOD OF TREATING LEADING-IN WIRE Filed Jan. 5,1933

ZZ Lo ,7 l 19 /6 V l6 l3 fNI ENTUR. IZL VLLIAMH ZABEL H15 AT TURNEY Patented Feb. 26, 1935 UNITED STATES METHOD OF TREATING LEADING-IN WIRE William P. Zabel, Cleveland Heights, Ohio, assignor to General Electric Company, a corporation of New York Application January 5,

8 Claims.

My invention relates to incandescent electric lamps and similar articles. One of the objects of my invention is to provide means for increasing the useful life thereof. It has been observed,

particularly in gasfilled lamps, that the filament,

after it has been burned, tends to break apart in service in the vicinity of the points at which it is attached to the leading-in wires. This is probably due to the fact that occluded gases in the end portion of the said inner leading-in wires are driven out by the heat radiated from the filament and the said gases then attack the filament directly or combine with other gases such as the occluded gases in the bulb and other glass parts which then attack the filament. According to my invention this action is substantially averted by purifying and annealing the end portions of the said inner leading-in wires to drive out the said occluded gases and render the said end portions passive to oxidation. This purifying and annealing process has been applied to leading-in wires of nickel and alloys thereof with exceptionally good results, although it is not in any way limited to such wires.

The leading-in wire assembly comprises the aforementioned inner leading-in wire and an outer leading-in wire connected by a short length of wire having a coefficient of expansion substantially the same as that of the glass comprising the stem press of the lamp. According to present practice these lead wire assemblies are annealed as a whole and therefore require the use of a special, relatively expensive, material for the outer leading-in wire, such as silicon bronze, deoxidized copper or aluminum copper, since ordinary copper would become brittle if subjected to the annealing heat. The temperature at which the assembly may be annealed is limited by the copper of the outer lead wire as well as the nickel, or other material of the inner lead wire. Too high a temperature makes the copper stick and renders it too soft for use on automatic machines. The nickel also has a tendency to stick. In either case it is necessary to roll and inspect all leads before they can be used. By annealing only the tips of the inner leading-in wires, these objections are overcome. Much higher temperatures may be employed and common copper may be used for the outer leads, since they are not subjected to the annealing heat. It is not desirable to apply these higher temperatures to the entire length of the leading-in wires either, since this would render them soft and subject to distortion in a lamp subjected to shocks or vibrations, with a resultant displacement of the filament from its normal position. I therefore prefer to purify and anneal only that end of the leading-in wires to which the filament is connected. One of the resulting features of this process is an inner leading-in wire in which a portion of the end to which the 1933, Serial No. 650.299

filament is connected, is soft with respect to the remainder thereof, thereby providing a yielding support for the said filament so that it will not be torn loose when the lamp is subjected to shocks and vibrations, while the said remainder of the leading-in wire, being relatively hard and rigid, retains the filament in its position. The soft annealed tip is also of advantage in the larger sizes of lead wires for the higher wattage lamps in which the wires are clamped around the filament by hand. Leads which are annealed according to present practice are too hard for this operation due to the fact that the annealing temperature is limited by the material of the outer leading-in wire. Additional features and advantages of my invention will appear from the following detailed description.

In the drawing Fig. 1 is a perspective view of an incandescent lamp; andFig. 2 is an elevation of apparatus used in the annealing of the leadingin wires.

In Fig. 1 is shown an incandescent lamp comprising a'base 10 and bulb 11 in which is sealed a filament 12 of a refractory metal such as tungsten. Said filament 12 is mounted in support wires 13 the ends of which are sealed in a button 14 on a support rod 15. Each end of the filament 12 is connected to the end of an inner leadingin wire 16 the other end of which is sealed in the press 17 of a stem tube 18. The said inner leading-in wires 16 are preferably made of nickel or alloys thereof, such as manganese nickel. The ends of said lead wires 16 are connected to press leads 19 which are embedded in the stem press 1'7 and are made of a metal having a. coefficient of expansion substantially the same as that of the glass comprising said press 17. The other ends of the said press leads 19 are connected to outer leading-in wires 20 which may be made of copper and are connected to the base shell 10 and a button 21 mounted thereon and insulated therefrom. The bulb 11 is evacuated through a hole 22, at the junction of the stem tube 18 and press 17, and an exhaust tube 23 communicating therewith. In the case of a gas-filled lamp, the bulb 11 is also filled through said tube 18 with an inert gas such as argon or nitrogen or a mixture of such gases.

The end of the inner leading-in wire 16 to which the filament 12 is connected is purified and annealed. The annealing may be carried out by the direct heat of the flame of a non-oxidizing gas, preferably a reducing gas such as hydrogen. This may be done as shown in Fig. 2 by placing the lead wire assembly, comprising preferably a nickel or nickel alloy inner lead wire 16, a press lead wire 19, and a copper outer lead wire 20, in a tube 24 which is horizontally mounted in a standard 25. The said lead wire 16 is placed in the said tube 24 so that the end thereof projects about an inch beyond the end of said tube, de-

pending upon the length of said wire. A gas, preferably hydrogen, is caused to flow through the tube 24 and is ignited at the end of said tube, the flame surrounding a portion of the exposed end of the wire 16. An additional hydrogen flame may be directed on said exposed end of Wire 16 by a burner 26 located therebelow to supply additio"al heat and to assure a complete surrounding of said wire. The end of the wire 16 is thus heated to a temperature greater than 700 C. approxi-' mately 1100 C. in the case of a nickel wire. A heating time of not more than one or two minutes has been found sufficient to carry out the work of purification and annealing. As can be seen in the drawing, the unheated portions of the lead wire assembly are located within the tube 24 so that the gas flowing therethrough keeps said unheated portions cool and prevents oxidation thereof. After the lead tip has been heated a suflicient time, a sleeve 27 surrounding the tube 24 is slid forward to the position shown in dotted lines so that the end thereof extends beyond the tip of the wire 16, thereby causing the flame to burn beyond the said tip of said wire. The flames of both the burner 26 and tube 27 are then extinguished, but the flow of gas through the tubes 24-27 is not interrupted, thereby allowing the dry hydrogen to pass over the hot end of wire 16 and cool it without oxidation. After a few minutes of cooling, the sleeve 27 is pushed back over the tube 24 and the lead wire assembly is removed. The treated end of wire 16 is then very soft compared to the remainder thereof. In the case of very heavy lead wires which tend to crack the glass stems while being bent to shape, it may be desirable to anneal the remainder thereof in the ordinary hydrogen annealing furnace at a temperature of about 750 C. to 800 C,

I do not wish to limit myself in any way to the method outlined above since I have obtained good results by heating the end of the inner leading-in wire by the passage of an electric current therethrough in an'atmosphere of a non-oxidizing gas or in a vacuum. It is also possible to treat the leads with radiated or conducted heat from a muffle or electric tube furnace or by inserting said ends in an induction coil in a non-oxidizing atmosphere.

The purifying and annealing process described above renders the end portions of the inner leading-in wires passive to oxidation. This is easily demonstrated by heating a treated lead wire below a red heat in air, as by passing an electric current therethrough. The treated end portion will maintain a relatively clean metallic appearance whereas the remainder of the wire will become noticeably tarnished.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. In an incandescent electric lamp or similar article comprising a bulb having a filament sealed therein, an inner leading-in wire in said bulb connected at one end to said filament, a portion of said end only of said inner leading-in wire being in a soft annealed condition and passive to oxidation.

2. In an incandescent electric lamp or similar article comprising a bulb having a filament sealed therein, a pair of inner leading-in wires in said bulb each connected at one end to said filament, portions of said ends only of said inner leading-in wires being in a soft annealed condition and passive to oxidation.

3. In an incandescent electric lamp or similar article comprising a bulb having a filament sealed therein, a nickel inner leading-in wire in said bulb connected at one end to said filament, a portion of said end only of said inner leading-in wire being in a soft annealed condition and passive to oxidation.

4. The method of treating a leading-in wire assembly for electric lamps and similar articles comprising an inner leading-in wire and an outer leading-in wire connected by a short length of press lead wire, which comprises purifying and annealing a portion of the free end only of said inner leading-in wire in a non-oxidizing atmosphere.

5. The method of treating a leading-in wire assembly for electric lamps and similar articles comprising a nickel inner leading-in wire and a copper outer leading-in wire connected by a short length of press lead wire, which comprises purifying and annealing a portion of the free end only of said inner leading-in wire in a non-oxidizing atmosphere.

6. The method of treating a leading-in wire assembly for electric lamps and similar articles comprising an inner leading-in wire and an outer leading-in wire connected by a short length of press lead wire, which comprises heating a portion of the free end only of said inner leading-in wire in the flame of a reducing gas to a high temperature sufficient to purify and anneal said end portion, then allowing a flow of said reducing gas to pass over said end portion to cool it.

7. The method of treating a leading-in wire assembly for electric lamps and similararticles comprising an inner leading-in wire and an outer leading-in wire connected by a short length of press lead wire, which consists in disposing said leading-in wire assembly in a tube with a portion of the free end only of said inner leading-in wire extending beyond the end of said tube, passing an inflammable reducing gas through said tube, said gas being ignited at the said end of said tube to heat the said exposed end portion of said inner leading-in wire sufiiciently to purify and anneal it, and then producing a relative movement between said tube and leading-in wire assembly to cause said assembly to lie wholly within said tube, thereby allowing the flow of reducing gas in said tube to pass over said end portion of said inner leading-in wire and cool it down.

8. The method of treating a leading-in wire assembly for electric lamps and similar articles comprising an inner leading-in wire and an outer leading-inwireconnected by a short length of press lead wire, which consists in disposing said leading-in wire assembly in a tube with a portion of the free end only of said inner leading in wire extending beyond the end of said tube, passing an inflammable reducing gas through said tube, said gas being ignited at the said end of said tube, providing a second flame of a reducing gas to heat the said exposed end portion of said inner leading-in wire sufficiently to purify and anneal it, and then producing a relative movement between said tube and leading-in wire assembly to cause said assembly to lie wholly within said tube, thereby allowing the flow of reducing gas in said tube to pass over said end portion of said inner leading-in wire and cool it down.

WILLIAM P. ZABEL. 

